Scanning method and apparatus applicable to variable magnification copying machines

Abstract

In a variable magnification copying machines capable of performing slit exposure of the image of original document to the surface of a photoconductor with a desired magnification by moving a contact glass on which the original document is placed or an optical system in synchronization with the photoconductor which is moved at a predetermined constant speed, a scanning method and apparatus in which the moving speed of the optical system or of the contact glass at the exposure step and the moving speed of the same at the returning step to the original position thereof are made variable depending upon a selected magnification of the copy of the original document, and the moving speed of the optical system or of the contact glass is set in such a manner that the sum of the time required for the optical system or the contact glass to move for exposure scanning and the time required for the optical system or the contact glass to return to the home position thereof is constant regardless of the selected magnification of the copy of the original document.

What is claimed is: 
     
       1. In a scanning method applicable to variable magnification copying machines capable of performing slit exposure of the image of original document to the surface of a photoconductor with a desired magnification by moving a contact glass on which said original document is placed or an optical system in synchronization with said photoconductor which is moved at a predetermined constant speed, the improvement in which the moving speed of said optical system or of said contact glass at the exposure step and the moving speed of the same at the returning step to the original position thereof are made variable depending upon a selected magnification of the copy of said original document and the moving speed of said optical system or of said contact glass is set in such a manner that the sum of the time required for said optical system or said contact glass to move for exposure scanning and the time required for said optical system or said contact glass to return to the home position thereof is constant regardless of said selected magnification of the copy of said original document. 
     
     
       2. A scanning method applicable to variable magnification copying machines as in claim 1, in which the moving speed of said optical system or of said contact glass is set so as to satisfy the equation of ##EQU13## wherein L is the distance of one way for said optical system or said contact glass to move for exposure scanning and m is said selected magnification of the copy of said original document and N is the number of copies to be made per minute and δT is the time loss (sec) which is regularly caused in each scanning and V F  is said moving speed (mm/sec) of said photoconductor and said optical system or said contact glass at the exposure step with unit magnification and υ B  is the moving speed (mm/sec) of said optical system or of said contact glass at the returning step thereof to the home positions thereof. 
     
     
       3. In a variable magnification copying machine capable of performing slit exposure of image of original document to the surface of a photoconductor with a desired magnification by moving a contact glass on which said original document is placed or an optical system in synchronization with said photoconductor which is moved at a predetermined constant speed, a scanning apparatus having speed changing mechanism capable of moving said optical system or said contact glass at speeds which satisfy the equation of ##EQU14## wherein L is the distance of one way for said optical system or said contact glass to move for exposure scanning, and m is said selected magnification of the copy of said original document, and N is the number of copies to be made per minute, and δT is the time loss (sec) which is regularly caused in each scanning, and V F  is said moving speed (mm/sec) of said photoconductor and said optical system or said contact glass at the exposure step with unit magnification, and υ B  is the moving speed (mm/sec) of said optical system or of said contact glass at the returning step thereof to the home position thereof. 
     
     
       4. A scanning apparatus as in claim 3, in which said speed changing mechanism comprises a combined mechanism of gears and clutches capable of transmitting rotating force input to an input section of said mechanism to said optical system or to an output section for driving said contact glass with a predetermined speed changing ratio and in a predetermined rotating direction.